/*
 * The contents of this web application are subject to the Mozilla Public License Version 
 * 1.1 (the "License"); you may not use this web application except in compliance with 
 * the License. You may obtain a copy of the License at http://www.mozilla.org/MPL/.
 * 
 * Software distributed under the License is distributed on an "AS IS" basis, 
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License 
 * for the specific language governing rights and limitations under the License.
 * 
 * The Original Code is owned by and the Initial Developer of the Original Code is 
 * Composite A/S (Danish business reg.no. 21744409). All Rights Reserved
 * 
 * Section 11 of the License is EXPRESSLY amended to include a provision stating 
 * that any dispute, including but not limited to disputes related to the enforcement 
 * of the License, to which Composite A/S as owner of the Original Code, as Initial 
 * Developer or in any other role, becomes a part to shall be governed by Danish law 
 * and be initiated before the Copenhagen City Court ("K�benhavns Byret")            
 */

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;


namespace Composite.Core.Linq
{
    internal static class TypeHelpers
    {        
        public static Type FindElementType(Expression expression)
        {
            Type elementType = expression.Type;
            if (!elementType.IsGenericType)
            {
                return null;
            }
            
            Type defintion = elementType.GetGenericTypeDefinition();

            if ((typeof (IQueryable<>) == defintion) ||
                (typeof (IEnumerable<>) == defintion))
            {
                return elementType.GetGenericArguments()[0];
            }
            
            Type[] interfaces = elementType.GetInterfaces();

            foreach (Type interf in interfaces)
            {
                Type def = interf;
                if (interf.IsGenericType)
                {
                    def = interf.GetGenericTypeDefinition();
                }

                if ((typeof (IQueryable<>) == def) ||
                    (typeof (IEnumerable<>) == def))
                {
                    return elementType.GetGenericArguments()[0];
                }
            }

            throw new NotImplementedException("Expression type could not be found");
        }
    }
}
